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machine/rp2040: wait for 1000 us after flash reset to avoid issues with busy USB bus #3821

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Merged
merged 1 commit into from
Jul 7, 2023
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machine/rp2040: wait for 1000 us after flash reset to avoid issues with busy USB bus #3821

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9 changes: 9 additions & 0 deletions src/machine/machine_rp2040_usb_fix_usb_device_enumeration.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
package machine

import (
"device/arm"
"device/rp"
)

Expand Down Expand Up @@ -87,6 +88,7 @@ func hw_enumeration_fix_force_ls_j() {
rp.USBCTRL_REGS.USB_MUXING.Set(rp.USBCTRL_REGS_USB_MUXING_TO_DIGITAL_PAD | rp.USBCTRL_REGS_USB_MUXING_SOFTCON)

// LS_J is now forced but while loop here just to check
waitCycles(125000)
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@sago35 sago35 Jul 6, 2023

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waiteCycles() should be added to the line above hw_enumeration_fix_finish().
As much as possible, it should be in the same form as the pico-sdk.

https://github.com/raspberrypi/pico-sdk/blob/6a7db34ff63345a7badec79ebea3aaef1712f374/src/rp2_common/pico_fix/rp2040_usb_device_enumeration/rp2040_usb_device_enumeration.c#L130

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@sago35 sago35 Jul 6, 2023

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Then, waitCycle(125000) waits for about 6ms.
It might be better to use a shorter value of about 125000 / 5.

image

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@ysoldak ysoldak Jul 10, 2023

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Use CPU clock constant?


// if timer pool disabled, or no timer available, have to busy wait.
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@ysoldak ysoldak Jul 10, 2023

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Comment become broken in two parts

hw_enumeration_fix_finish()
Expand All @@ -109,3 +111,10 @@ func hw_enumeration_fix_finish() {
// Restore the pad ctrl value
padsBank0.io[dp].Set(padCtrlPrev)
}

func waitCycles(n int) {
for n > 0 {
arm.Asm("nop")
n--
}
}